Standard 25 mm
Pneumatic Vice Action Grip
Pneumatic vice action grips clamp the full specimen width at a constant, even pressure — which is what stops one side slipping or tearing before the other.
SpecificationsTesting standard
ISO 4674-1
Rubber- or plastics-coated fabrics — Determination of tear resistance — Part 1: Constant rate of tear methods
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 4674-1 specifies two methods for the forces needed to initiate and propagate tearing in a rubber- or plastics-coated fabric at a constant rate of tear: method A, the tongue tear, and method B, the trouser tear.
At a glance
- Test type
- Tear — a cut or nick is forced to grow
- Published by
- ISO
- Edition
- ISO 4674-1:2016
- Runs on
- Series 7200 and Series 9000
What the test does
A conditioned specimen of coated fabric is cut in the warp or weft direction and prepared as one of two geometries. Method A is a tongue tear, cut so that two tear fronts propagate at once. Method B is a trouser tear, a single slit along which one tear runs. Either is pulled at a constant rate of tear while the whole force trace is recorded, and the tear force is read from that trace by the rule the method gives for the geometry used — not simply as its highest point.
What it measures, and why it matters
Whether damage spreads. This is the property that actually governs the life of a coated fabric: an architectural membrane, a tarpaulin, an awning or a truck curtain almost never fails by being pulled apart in a clean sheet. Something catches it, a fixing works loose, a stone punctures it — and what decides the outcome is whether the resulting hole stays a hole or runs into a split. Tensile strength describes a condition the product rarely experiences, which is why tear resistance and tensile strength are specified together and neither substitutes for the other.
Tongue or trouser
Two geometries, two tear fronts, two different numbers from the same material.
- Method A
- Tongue tearA double tongue, so two tear fronts run at once — closer to how a tear propagates in a tensioned membrane.
- Method B
- Trouser tearA single tear front along a slit, the same geometry used for films and rubber.
- Measures
- The forces to initiate and to propagate a tear
- Rate
- Constant rate of tear
- Directions
- Warp and weft, separatelyThe base fabric is woven and directional, and the coating does not change that.
- Record which method was used
- Every timeDakA and B are not interchangeable and a value without the letter cannot be checked against a specification.
Coated fabric tear is the property that decides whether a puncture in a membrane or a tarpaulin stays a hole or becomes a split. It matters more in service than tensile strength does.
Test speed
- Rate
- Constant rate of tear
- Reported
- Tear force, by the method's rule for reading the trace
- Trace
- Retained — coated fabric tears in a saw-tooth as each yarn gives way
- Watch for the coating splitting ahead of the fabric
- DakOn a heavily coated cloth the coating can fail before the yarns, and the trace then describes the coating.
Calculations
Tear force—
Read from the trace by the method's rule for the geometry used
Not simply the highest point. Each yarn rupture is a peak, and the rule exists so two laboratories read the same saw-tooth the same way.
Why tongue and trouser differ—
Two simultaneous tear fronts against one
The tongue geometry propagates two tears at once and distributes the work differently, so it does not produce the trouser number on the same cloth.
How the test runs
- 01Condition the coated fabric as specified.
- 02Choose method A or method B from the specification.
- 03Cut specimens in the warp and weft directions.
- 04Cut the tongues or the slit cleanly with a sharp blade in one pass.
- 05Fit pneumatic grips at a pressure that holds without cutting the coating.
- 06Mount the tongues or legs squarely.
- 07Separate at the specified constant rate of tear.
- 08Record the whole trace as the tear propagates.
- 09Read the tear force by the rule for the geometry used.
- 10Note whether the coating split ahead of the yarns.
- 11Report the method letter and the direction with every value.
The fixture this method needs
What the report has to contain
- Reference to ISO 4674-1 and the edition
- Which method was used — A or B
- Fabric identification, coating type and mass per unit area
- Direction tested
- Conditioning atmosphere
- Rate of tear
- Tear force for each specimen and how the trace was read
- Mean and variability by direction
- Whether the coating failed ahead of the substrate
- Number of specimens rejected and why
What the machine must be capable of
Modest force with a faithful data record. Coated fabric tear forces commonly run from tens to a few hundred newtons, and the trace matters as much as the peak — the tear advances yarn by yarn, so the record is a saw-tooth and the method's reading rule is what makes two laboratories agree on it. Grips need to hold a slick coated surface at a pressure that does not cut through the coating into the substrate, which is the same narrow window ISO 1421 has to find.
What goes wrong in practice
Reporting a tear force without the method letter, when tongue and trouser give different numbers on the same cloth. Averaging warp and weft. Reading the single highest peak from a saw-tooth trace rather than applying the method's rule. A ragged starting cut. And missing the case where the coating split ahead of the yarns — that is a real observation about the product, but the resulting force describes the coating rather than the reinforced composite, and a reader needs to be told which happened.
ISO 4674-1 or ISO 1421
| ISO 4674-1 — tear | ISO 1421 — tensile | |
|---|---|---|
| Question | Does damage spread? | How much load does it carry? |
| Failure | A tear runs | The fabric breaks |
| Predicts the other | No | No |
| Specified together | Usually | Usually |
Tensile strength describes an unblemished sheet. A membrane or a tarpaulin almost never fails that way — something catches it, and tear resistance decides what happens next.
Questions we are asked about this test
What is ISO 4674-1?
It is the ISO tear resistance method for rubber- or plastics-coated fabrics using a constant rate of tear. It specifies two methods: method A, the tongue tear, and method B, the trouser tear. Both determine the forces needed to initiate and to propagate tearing. The current edition is ISO 4674-1:2016, superseding the 2003 edition.
What is the difference between tongue and trouser?
The number of tear fronts. A trouser specimen has a single slit and one tear runs along it, the same geometry used for films and solid rubber. A tongue specimen is cut so that two tear fronts propagate at once, which distributes the work differently and is closer to how a tear behaves in a tensioned membrane. They do not give the same number on the same cloth, so the method letter belongs with every value.
Why does tear matter more than tensile for a coated fabric?
Because that is how these materials actually fail. An architectural membrane, a tarpaulin, an awning or a truck curtain almost never fails by being pulled apart in a clean sheet — something catches it, a fixing works loose, a stone punctures it, and what decides the outcome is whether that damage stays a hole or runs into a split. Tensile strength describes a condition the product rarely experiences.
Why is the trace saw-toothed?
Because the tear advances yarn by yarn. Each yarn in the base fabric resists, then ruptures, and the load falls before building against the next, so the record is a series of peaks rather than a smooth curve. That is why the method specifies how to read the force from the trace — taking the single highest point would report whichever yarn happened to be strongest.
What if the coating fails before the fabric?
It is worth noting in the report, because the trace then describes the coating rather than the composite. On a heavily coated cloth the coating can split ahead of the yarns, and the force required to do that is not the same as the force to tear the reinforced material. It is a real observation about the product rather than a failed test, but a reader needs to know which happened.
Why test warp and weft separately?
Because the base fabric is woven and therefore directional, and coating it does not remove that. Warp and weft yarns differ in count, tension and crimp from manufacture, so a coated fabric tears at different forces in the two directions — often substantially. A membrane is engineered around that difference and an average would describe neither axis.
How does it relate to ISO 1421?
They are the two halves of specifying a coated fabric's mechanical behaviour, and neither predicts the other. ISO 1421 measures how much load the material carries before it breaks; this measures whether damage in it spreads. Both usually appear in the same specification, alongside ISO 2411 for whether the coating stays attached at all.
Running ISO 4674-1 on the Series 7200 and Series 9000
Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.
| The method asks for | Dak supplies | |
|---|---|---|
| Capacity | Low to moderate — coated fabric tear forces commonly run from tens to a few hundred newtons | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | Class 1 over the working range | ISO 7500-1 Class 0.5, verified to ASTM E4, DIN 51221 and BS 1610 |
| Gripping | Grips holding the tongues or the trouser legs, wide enough for the specimen | Wedge, vice-action, pneumatic and hydraulic grips, built to the specimen |
| Environment | 23 ± 2 °C standard laboratory atmosphere | 3009 series chambers, −150 °C to +400 °C — temperature only |
This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.